The human brain is highly sensitive to perturbations in oxygen and blood glucose levels. Cerebral hypoxia (i.e., reduced oxygen to the brain) is marked by uncontrolled movement, inability to focus, and changes in behavior. Changes in blood glucose levels are also marked by alterations in cognition. For instance, hypoglycemia can lead to function brain failure, which includes changes in behavior and coma (Philip Cryer. (2007) J Clin Invest. 117(4):868-870). Hyperglycemia, on the other hand, has been associated with slowing of all cognitive performance tests and an increased number of mental subtraction errors (Cox et al. (2005) Diabetes Care. 28(1):71-77).
There are many events that can lead to alterations in blood glucose and/or oxygen levels in the brain. These conditions include diabetes type 1 and type 2, hepatitis, kidney disease, medications, and endocrine deficiencies. Concussions are also an example of an event that can cause both localized and systemic alterations in oxygen and glucose levels in the brain. There are approximately four to five million concussions in the United States each year (Iverson et al. (2004) Brain Injury. 18(5):433-43). Many of these concussions occur in contact sports such as American football and ice hockey. Nevertheless, concussions have been identified in other sports such as baseball, soccer, and basketball. Concussions have also been a source of concern in the armed forces as well. Concussions, therefore, are a health risk for almost all athletes—both professional and amateur and soldiers.
At present, there are several methods of detecting a concussion in an individual. One method is a medical examination performed immediately after the concussion occurs. This methodology requires a medical professional to administer an examination to an individual—taking account of the individual's mental faculties as well as the individual's response to certain stimuli. In addition, the medical professional may utilize CT scans to identify brain damage if the individual appears to have a concussion. Other methods of detecting concussions include Post-Concussion Symptom Scale (PCSS), Balance Error Scoring System (BESS), and the five subscales of the Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT). The most prevalent of these tests is the ImPACT testing regimen.
However, these detection methodologies have substantial drawbacks when an athlete, soldier, or other individual suffers a potential concussion in the field and requires immediate and reliable information. The medical examination lacks reliability due to the subjectivity of the examination and can take a significant amount of time to perform. When performing the examination, the medical professional is left to determine whether the individual suffered a concussion without any prior information regarding the subject's history. Regarding the CT scan, the device is not readily available outside of medical facilities.
The other methods lack reliability or reproducibility. A study of these methods established that “there is poor concurrent validity among three commonly used concussion tests and there is no baseline score that predicts whether post-concussion syndrome will occur” (Barlow et al. (2011) Int J Sports Phys Ther. 6(4):361-371). In other words, the validity of the most commonly used tests for concussions has not been established.